The rapidly increasing application of ultrasonic technology for both diagnostic and therapeutic purposes has drawn attention to the lack of precise information on the biological effects of exposure to ultrasonic irradiation. Studies to date have been uncoordinated and lack reliable and quantitiative dosimetric measurements. An integrated effort by both physical and biological scientists to investigate ultrasonic instrumentation and dosimetry, kinetics and dose-response relationships, cellular histochemistry, cytogenetic assays, ultrastructural alterations and changes in cell division rates, and effects on reproductive physiology and embryogenesis is proposed. This program is designed to determine quantitatively the threshold levels of injury that are urgently needed and are of significant public health concern.